FontMeter

FontMeter is a free browser extension that shows the type system of any web page, right on the page. Click the icon and every text style gets a small label with its size. A panel lists every style, the fonts the browser really renders (with fallbacks, faked bold and unused @font-face rules flagged), the type scale with its closest modular ratio (export as CSS variables, Tailwind v4 @theme or JSON tokens) and WCAG contrast for every style. Inspect margins and padding, measure distances and pick any pixel's color. It runs only in the tab you turn it on, with no servers, analytics or account. Try every tool on fontmeter.dev before installing.